Wireless Local Area Network (WLAN)-enabled mobile communication devices are in use today. In a WLAN, access points (sometimes also called “base stations”) with wireless interfaces are scattered. Each mobile communication device runs a search (or a scan), for example, to see if there is an available access point located nearby. If detecting an access point meeting a predetermined condition and having received signal strength equal to or greater than a connection threshold, the mobile communication device connects to the access point automatically or according to an instruction from the user to thereby perform wireless communication.
In an area where a plurality of access points are densely deployed, a mobile communication device may be able to perform a handover from one to another among the access points as the mobile communication device moves. For example, there has been proposed a handover scheme in which, when the received signal strength of a currently connected access point becomes low, a mobile communication device performs data communication and a scan for neighboring access points in parallel by time division and, then, performs a handover to a different access point with higher received signal strength.
In addition, there has been proposed a wireless communication system for reducing power consumption of a mobile communication device by shortening the time for scanning in the case where the mobile communication device performs a handover. According to the wireless communication system, when having performed a scan, the mobile communication device records simultaneous detection information indicating a plurality of access points detected by the scan at the same time. Later when being connected to an access point, the mobile communication device skips a scan for neighboring access points by extracting, from the simultaneous detection information, handover destination options likely to be detected simultaneously with the currently connected access point.
Further, there has been proposed a mobile communication device enabling voice calls and data communication via a WLAN. The mobile communication device stores in advance a profile associating identification information of each access point and a type indicating whether the access point supports voice calls. Based on the profile, the mobile communication device determines whether each of neighboring access points supports voice calls, and sets the scan time for access points supporting voice calls longer than that for access points not supporting voice calls.
See, for example, Japanese Laid-open Patent Publication Nos. 2005-175932, 2010-81118, and 2011-250342.
Note here that, around an access point, there may or may not be another access point to which a handover is possible from the access point. In shopping malls and large offices, for example, it is sometimes the case that a plurality of access points are densely deployed by the same installer so as to cover a large area with a WLAN. Each of such a plurality of access points is usually connectable from the same mobile communication device, and handovers among the access points are allowed in general. On the other hand, in private residences and small retail premises, for example, an installer may install only a single access point because only a specific small area needs to be covered with a WLAN. Around such a singularly installed access point, no other access point may be present. Even if a different access point exists, it is often the case that the same mobile communication device is not allowed to connect to the access point and thus a handover is not possible.
Therefore, if the mobile communication device initiates a scanning operation in preparation for a handover on a continuous basis, the scanning operation ends up being wasted when a different access point to which a handover is possible does not exist in its neighboring area, thus putting more load on the mobile communication device. For example, as described in Japanese Laid-open Patent Publication No. 2005-175932, continuing search for neighboring handover destinations while being connected to an access point results in high power consumption of the mobile communication device. In addition, performing data communication and a search for handover destinations in parallel by time division may lead to decreased quality of the data communication.